1. Field of the Invention
The present invention relates to an information processing apparatus having a plurality of power modes, and more particularly to shifting between a plurality of power modes.
2. Description of the Related Art
In recent years, as an image forming apparatus, which is an example of an information processing apparatus, is multi-functionalized, the construction thereof becomes complicated, and it takes more time to start up the image forming apparatus.
To solve this problem, there have been proposed various techniques for reducing time taken to start up the image forming apparatus (see e.g. Japanese Patent Laid-Open Publication No. 2006-92474).
The information processing apparatus disclosed in Japanese Patent Laid-Open Publication No. 2006-92474 has a standby mode, a first energy saving mode, and a second energy saving mode, as power modes thereof. When the information processing apparatus is in the first energy saving mode, only a RAM and the minimum number of devices necessary for returning from the first energy saving mode are energized. Further, in the first energy saving mode, return data (first return data) necessary for returning from the first energy saving mode are stored in the RAM, and when a return event causing a return from the first energy saving mode occurs, the information processing apparatus returns from the first energy saving mode to the standby mode based on the return data stored in the RAM. Further, when the information processing apparatus is in the second energy saving mode, only the minimum number of devices necessary for returning from the second energy saving mode are energized. In the second energy saving mode, the information processing apparatus stores in advance return data (second return data) necessary for returning from the second energy saving mode in a hard disk, and when a return event causing a return from the second energy saving mode occurs, the information processing apparatus returns from the second energy saving mode to the standby mode based on the return data stored in the hard disk.
When shifting from the standby mode to the first energy saving mode, the disclosed information processing apparatus stores the first return data in the RAM, and stores the second return data in the hard disk. If the power switch is turned off in the first energy saving mode, the information processing apparatus shifts to the second energy saving mode. Then, when a return event causing a return from the second energy saving mode occurs, power is supplied to the whole information processing apparatus, and the information processing apparatus returns to the standby mode based on the second return data stored in the hard disk.
To cause the information processing apparatus to return from the second energy saving mode to the standby mode, the second return data read from the hard disk is restored in the RAM, and then the information processing apparatus is caused to return to the standby mode based on the second return data. In this information processing apparatus, however, it takes time to restore the second return data stored in the hard disk in the RAM. Therefore, in the case of the information processing apparatus disclosed in Japanese Patent Laid-Open Publication No. 2006-92474, if the power switch is turned off in the first energy saving mode to cause the apparatus to shift to the second energy saving mode, it takes time before the information processing apparatus returns to the standby mode.